GB2440738A

GB2440738A - Electroluminescent fabric

Info

Publication number: GB2440738A
Application number: GB0615761A
Authority: GB
Inventors: Tilak Dias; Ravindra Marks Monaragala
Original assignee: University of Manchester
Current assignee: University of Manchester
Priority date: 2006-08-08
Filing date: 2006-08-08
Publication date: 2008-02-13
Also published as: CN101528997A; WO2008017810A1; US20100003496A1; GB0615761D0; EP2049716A1

Abstract

A fabric 2, preferably knitted, comprises at least two electrodes 4,6 [16,18 Fig. 3] at spaced apart locations to define a space in between which at least one layer of electroluminescent material 12 [20 Fig. 3] is located. Conductive pathways 8,10 connect the electrodes 4,6 to a power supply such that when power is supplied the electroluminescent layer illuminates. In one embodiment, the electroluminescent material may take the form of a coating on conductive fibres [30, Fig. 5]. The fibres are arranged parallel to one another and when a current is passed through them an electric field is created between adjacent yams causing them to luminesce. A yarn 30 for use in such fabric is disclosed and comprises a conductive core with a layer of electroluminescent material coated thereon. The material will normally comprise encapsulated phosphor. A protective polymeric layer may be coated over the electroluminescent material. A method of making the yarn is provided.

Description

I

ELECTRO-LUMINANT FABRIC STRUCTURES

This invention relates to electro-luminant materials: to the creation of illuminated zones or areas at a fabric surface, and to yarns for use in such fabrics. The invention has particular, but not exclusive application to knitted fabrics.

Electro-luminant materials are known. Essentially, such a material comprises a substance which luminesces upon exposure to an electric field.

Typically, the substance comprises phosphor. DuPont has produced a range of electro-luminescent inks or pastes under the name LUXPRINT. In these materials, phosphors are microencapsulated to protect them against moisture, with the encapsulated phosphors held in a binder to form an ink or paste.

This range of materials luminesces when subject to an electric field of 60 to volts AC, at frequencies in the range 50 to 1000 Hz. A preferred operating range is 80 to 120 volts AC at 400 Hz.

The DuPont materials referred to above have been used in laminar structures, sandwiched between what are effectively two sheet electrodes.

One of the electrodes is in the form of a translucent conductive ink such that when the field is applied, the luminescing phosphor is visible through the translucent ink electrode.

In the DuPont material structure as referred to above, the electrical field is created perpendicular to the plane of the laminar structure; ie, between the sheet electrodes at either surface. We have found that a layer of electro-luminescent material of the kind referred to above can be caused to luminesce in an electric field created over a surface rather than one created perpendicularly across it. According to the invention, a sheet product has two electrodes incorporated at spaced locations thereon to define a surface area therebetween. A layer of electro-luminescerit material is disposed in this area, and conductive pathways are provided on the product for connecting the d electrodes to a source of electrical power. When the power is applied, it creates an electrical field in the area, and causes the material to luminesce at the surface.

Preferred products according to the invention are fabrics; woven, knitted or stitch-bonded, but most preferably knitted. The electrodes can be mounted at the product surface, but where the product is a fabric the electrodes are preferably incorporated within the structure of the fabric. In such an embodiment, the electrodes may comprises yarns which themselves form components of the fabric.

The connections to the electrodes can take any suitable form, but once again when the product is a fabric of some kind, conductive pathways can readily be formed in the fabric during its manufacturing process.

It will be appreciated that whatever the shape or orientation of the electrodes, in products of the invention the luminescent area created is dependent entirely upon the shape and extent of the layer of electro-luminescent material in the area between the electrodes. The electro-luminescent material can of course substantially fill that area, but can create different shapes within it. The electrodes can be elongate and extend along a boundary of the layer of the material. Generally, the electrodes will be linear and define a polygonal, not necessarily right angular, area therebetween.

In addition to providing means for luminescing different shapes within the area defined by the electrodes, the colour and intensity of the light generated can also be varied by using different luminescent materials, and different densities thereof within the electroluminescent material layer.

Normally the electro-luminescent material will be of the kind described above from DuPont, but the present invention also contemplates phosphor particles being held either individually or in groups within the fabric. Phosphor particles may be encapsulated within the yarns of a fabric or within the filaments of multifilament yarns within a fabric, using the technique described in our International Patent Application No: G806/001 804.

The layer of electro-luminescent material may be a separate component in fabric according to the invention. It can though itself comprise individual yarns. Such a yarn according to the invention comprises a conductive core having a layer of electro-luminescent material coated thereon. The layer of electro-luminescent material is normally applied as an ink of the kind referred to above. The ink can be secured in place by baking, for example by exposure to Ultra-Violet (UV) light for a short period immediately after application. The exposure time will depend primarily on the diameter of the yams which could be mono-filament or multi-filament yarns and the intensity of UV applied. A further protective layer can be applied over the electro-luminescent layer, itself baked on by exposure to UV light. Coated yarns of this type can be activated to luminesce by application of a high AC voltage between two yarns in contact with each other.

In a knitted structure coated yarns of the kind just described can be brought into contact with one another according to a predetermined plan.

This means a variety of different luminescent designs can be created.

There are numerous applications for the present invention but a particular one is in garments. Where individuals have to work in dark conditions, and cannot rely on reflected light to identify them, products or fabrics embodying the invention can be effectively applied to their clothing.

Other applications would include floor, wall or ceiling coverings where lighted areas are required either for direct illumination such as in an automobile roof lining; a point identification on a wall such as a light switch in a darkened area; and identifying walkways or aisles in aeroplanes or theatres.

Embodiments of the invention will now be described by way of example and with reference to the accompanying schematic drawings, wherein: Figure 1 shows a plan view of a portion of sheet product according to the invention; Figure 2 is a sectional view taken on line A- A of Figure 1; Figure 3 is a plan view of a portion of sheet product according to a second embodiment of the invention; Figure 4 is a plan view similar to that of Figure 3 of a portion of sheet product according to a third embodiment of the invention; and Figure 5 is a plan view similar to that of Figure 3 of a portion of sheet product according to a fourth embodiment of the invention.

Figure 1 shows the surface of a sheet product 2 according to the invention. Elongate electrodes 4 and 6 are arranged in pairs on the surface, with electrodes 4 being connected along pathways 8, and electrodes 6 along pathways 10, to a source of electrical power (not shown).

Between each pair of electrodes on the surface of the product is applied an electro-luminescent material 12, such as a DuPont LUXPRINT ink of the kind referred to above. Where required, a protective layer can be applied over the luminescent material.

The spacing of the electrodes in sheet products of the invention will be determined in relation to the frequency of the voltage required to energise the electro-luminescent material. Higher voltages and higher frequencies will generally be required for greater electrode spacing, but this requirement may be mitigated by installing an insulator between the electrodes, or ensuring appropriate insulative characteristics of the base sheet product. As noted above, the invention can be particularly effectively applied to fabrics, and even more particularly to knitted fabrics. In a knitted fabric, the electrodes 4,6 as shown in Figures 1 and 2, and the conductive pathways 8, can be created by knitting courses and/or wales using conductive yarns. Suitable such yarns are made from multiple fine silver filaments. With such a fabric structure, it is preferred also to apply an insulative layer to the surface of the fabric opposite that upon which the luminescent material is applied, as well as over the luminescent material itself.

In the embodiment of Figure 3, electrodes 16 and 18 are effectively created by continuous adjacent silver courses. The electro-luminescent zones 20 are created by phosphor particles encapsulated within the fibres of a textile yarn using the technique described in our International Patent Application No: GB061001804, referred to above. In the knitted fabric illustrated, lengths of this specialist yarn can be incorporated in the respective zones without difficulty. The use of Jacquard knitting techniques and a positive yam delivery system of the kind disclosed in published Patent Specification No: GBO6IODI 804 facilitates precise positioning of the electro-luminescent zones 20, in accordance with a predetermined pattern. Where the electro-luminescent material is an ink of the kind referred to above, the pigment will normally be introduced into the binder.

Figure 4 illustrates a variation on the embodiment of Figure 3. In this embodiment, also using a knitted fabric, electro-luminescent particles are microencapsutated within individual polymeric yarns, either monofilament or multifilament yarns. These yarns are knitted between adjacent courses of conductive (silver) yarns 22,24 to form luminescent areas 26. The ratio of the number of electro-luminescent courses to the number of silver courses will influence the voltage and frequency required in the electric field between the courses to energise the respective electro-luminescent zones.

In the embodiment of Figure 5 an electro-luminescent zone 28 is created by yarns 30 each comprising a conductive core with a coating thereon of electro-luminescent material of the kind referred to above. The yarns extend between terminals 32 connected to a source 34 of alternating current through a circuit completed by a switch 36. When the switch is closed, the AC creates electric fields between adjacent, preferably touching yarns which cause them to luminesce.

Different colour and intensity effects can be created by introducing colour pigments and varying the density of particles in the luminescent material used. Colour pigments can be introduced during manufacture of the material itself. The particle density can also be controlled at this stage.

However, when the luminescent particles are encapsulated within the body of yarns when a fabric is produced, or coated on individual yarns, then of course the number of yarns used, and whether used alone or in combination with other yarns, is an additional factor.

The embodiments described above have focused particularly on knitted fabrics, but the invention is also applicable to other structures including woven, braided, stitch-bonded and other non-woven structures. The precise form of the electrodes and conductive pathways will of course depend upon the nature of the basic structure.

Claims

CLAIMS

1. A fabric having two electrodes incorporated at spaced locations thereon to define a surface area therebetween; a layer of electro-luminescent material in said area; and conductive pathways for connecting the electrodes to a source of electrical power to create an electrical field in said area and cause said material to luminesce.

2. A fabric according to Claim 1 wherein the electrodes are mounted at the fabric surface.

3. A fabric according to Claim I wherein the electrodes are incorporated in the fabric.

4. A fabric according to Claim 3 wherein the electrodes comprise yarns forming components of the fabric.

5. A fabric according to Claim 4 wherein the fabric is knitted.

6. A fabric according to any preceding Claim wherein the conductive pathways comprise component yarns of the fabric.

7. A fabric according to any preceding Claim wherein the layer of luminescent material comprises yarns having a fine layer of electro-luminescent material 8. A fabric according to Claim 7 wherein said yarns are monofilament yarns.

9. A fabric according to Claim 4 and to Claim 7 or Claim 8 wherein said yarns are electrically conductive and selectively connectable to a source of electrical power.

10. A fabric according to any preceding Claim wherein the layer of electro-luminescent material substantially fills said area.

11. A fabric according to any of Claims 1 to 9 wherein the layer of electro-luminescent material only partially fills said area.

12. A fabric according to any preceding Claim wherein the electrodes are elongate and extend along a boundary of the layer of material.

13. A fabric according to any preceding Claim wherein the electrodes are linear and define a polygonal area therebetween.

14. A fabric according to any preceding Claim wherein the electro-luminescent material comprises phosphor particles confined in a laminar structure.

15. A fabric according to any preceding Claim wherein the electro-luminescent material comprises encapsulated phosphor particles.

16. A fabric according to Claim 15 wherein the phosphor particles are encapsulated within yarns of the fabric.

17. A fabric according to Claim 16 wherein a plurality of particles are encapsulated at spaced locations along a length of at least one yarn.

18. A fabric according to any preceding Claim including a protective layer over the electro-luminescent material.

19. A garment comprising fabric according to any preceding Claim.

20. A yarn for use in a fabric to create an electro-luminescent area on the fabric, which yarn comprises a conductive core having a layer of electro-lum inescent material coated thereon.

21. A yarn according to Claim 20 wherein the electro-luminescent material comprises encapsulated phosphor.

22. A yarn according to Claim 20 or Claim 21 including a protective layer over the electro-luminescent material.

23. A yarn according to Claim 22 wherein the protective layer is polymeric.

24. A yarn according to Claim 22 or Claim 23 wherein the protective layer is baked on.

25. A yarn according to Claim 22 wherein the protective layer is baked on by exposure to Ultra-Violet light.

26. A yarn according to Claim 20 to 25 wherein the electro-luminescent material is baked on to the conductive core.

27. A yarn according to Claim 26 wherein the electro-luminescent material is baked on to the conductive core by exposure to Ultra-Violet light.

28. A fabric comprising a plurality of yarns according to any of Claims 20 to 27.

29. A method of making a yarn capable of electro-luminescence comprising coating a conductive yarn core with an electro-luminescent material.

30. A method according to Claim 29 including the step of baking the coated yarn core to secure the electro-luminescent material thereto.

31. A method according to Claim 30 wherein the electro-luminescent material is baked on by exposure to Ultra-Violet light.

32. A method according to any of Claims 29 to 31 including the step of applying a protective layer to the electro-luminescent coating.

33. A method according to Claim 32 wherein the protective layer is polymeric.

34. A method according to Claim 32 or Claim 33 wherein the protective layer is baked on to the yarn core bearing the coating of electroluminescent material.

35. A method according to Claim 34 wherein the protective layer is baked on by exposure to Ultra-Violet light.